linux-kernel - Re: [PATCH] x86, acpi memory hotplug, add parameter to disable memory hotplug

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Date:	Tue, 14 Jan 2014 10:26:27 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	Toshi Kani <toshi.kani@...com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linn Crosetto <linn@...com>, Pekka Enberg <penberg@...nel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tang Chen <tangchen@...fujitsu.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Dave Young <dyoung@...hat.com>, linux-acpi@...r.kernel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] x86, acpi memory hotplug, add parameter to disable
 memory hotplug

On Tue, Jan 14, 2014 at 06:05:15AM -0500, Prarit Bhargava wrote:

[..]
> >>> As mentioned, self-NAK.  I have seen a system that I needed to specify
> >>> memmap=exactmap & had hotplug memory.  I will only keep the acpi_no_memhotplug
> >>> option in the next version of the patch.
> >>
> >>
> >> Your following first patch is simply and makes sense.
> >>
> >> http://marc.info/?l=linux-acpi&m=138922019607796&w=2
> >>
> > 
> > In this option, it also requires changing kexec-tools to specify the new
> > option for kdump.  It won't be simpler.
> 
> It will be simpler for the kernel and those of us who have to debug busted e820
> maps ;)
> 
> Unfortunately I may not be able to give you the automatic disable.  I did
> contemplate adding a !is_kdump_kernel() to the ACPI memory hotplug init call,
> but it seems like that is unacceptable as well.

I think everybody agrees that there has to be a stand alone command line
option to disable memory hotplug.

Whether to tie it into memmap=exactmap and mem=X is the contentious bit.
So I would suggest that just post a patch to disable memory hotplut using
a command line and later more patches can go in if people strongly feel
the need to tie it into memmap=exactmap.

In the mean time, we will modify /etc/sysconfig/kdump to pass
acpi_no_memhotplug so that user does not have to worry about passing this
parameter and kexec-tools will not have to be modified either.

Thanks
Vivek
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